This competing supplemental application requests support for a significant expansion of the scope of the parent grant, the National Life Style, Health, and Aging Project (NSHAP), 1RO1 AG21487-01. The supplement will extend the population coverage of both NSHAP and the Health and Retirement Survey (HRS) by including within their scope households that would otherwise be excluded from consideration due to deficiencies in the sampling frame. Methodologically, the supplement will provide a benchmark comparison of the traditional listing process that has dominated survey sampling for 60 years with an alternative list-based methodology that has been explored only in the last few years. Substantively, the supplement will (i) determine the characteristics of households that would be excluded by either approach alone, and (ii) add to the dataset a representative sample of the households excluded by the traditional listing. An added advantage of the proposal is the collaboration between the leading samplers at the two major university-based social research organizations - the National Opinion Research Center at the University of Chicago, and the Institute for Social Research at the University of Michigan. The initiative provides a unique opportunity to advance survey research methodology while enhancing the quality of these two major NIA surveys. This may be the only opportunity that will arise to make a comprehensive comparison of the two frames for a nationally representative sample. By integrating the comparison with the fieldwork for NSHAP and HRS, a comparison of the two methods can be carried out on a national scale at relatively low marginal cost. To launch and execute such a comparison independently would cost between $1 million and $2 million. The timing of the project is ideal in that survey samplers and survey methodologists are in the process of debating whether and at what point a switch to the new approach should be made. [unreadable] [unreadable]